338 STUDIES IN ADVANCED PHYSIOLOGY. 



About ninety per cent, of the pancreatic juice is water. 

 Dissolved in it are the mineral salts, to which the alkalinity 

 of this juice is due, for unlike the gastric juice, the ferments 

 of the pancreatic juice can act in an alkaline medium only, 

 and not in an acid one. The pre-eminence of pancreatic 

 juice as a digestive agent, exceeding very much that of the 

 pepsin or ptyalin, is due to the presence of the three fer- 

 ments named, trypsin amylopsin and steapsin. 



Trypsin. Trypsin is a very powerful ferment changing 

 with great energy proteids into peptones. It is this ferment 

 which acts iipon all those proteids left unacted upon by the 

 stomach, and upon all of the intermediate stages left incom- 

 plete by the pepsin. Here, too, the change from the pro- 

 teids to the peptones is not a simple and direct one, there 

 being a number of intervening stages called here, also, pro- 

 teoses, the final resulting stage, however, being peptone in 

 no essential way distinguishable from the peptone made by 

 the stomach. The powerful digestive action of trypsin is 

 shown in the fact that some of "the peptone is disintegrated 

 still further into two substances called leudn and tyrosin, 

 substances which the chemist may readily detect where pan- 

 creatic digestion is going on, but the physiological signifi- 

 cance of which we are at present not at all able to under- 

 stand. The peptones are, of course, the source of the ni- 

 trogenous foods of the body, but why some of the peptones 

 should be broken up, that is, digested still further into 

 bodies like leucin and tyrosin, bodies which seem to play 

 no part as foods, is not at all clear. The trypsin is also able 

 to digest any albuminoids which may have escaped diges- 

 tion in the stomach. 



Amylopsin. Amylopsin is a ferment of the pancreatic 

 juice identical with the ptyalin of the saliva, and like this 

 ptyalin possesses the property of changing starch into mal- 

 tose. The pancreas is called by the Germans the "Ab- 

 dominal Salivary Gland," no doubt because of the identity 

 of its action on the starches, with the salivary glands. The 



